Semiconductor device driving units are conventionally used to generate a three phase AC voltage to drive a synchronous motor from a variable speed drive. Such a drive unit may be used in electric vehicles, although they have other uses in other fields. Semiconductor device driving units may employ a number of gate driven semiconductor devices, for example IGBTs (Insulated-Gate Bipolar Transistor) or MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor).